1. Field of the Invention
The present invention relates to an antenna apparatus, and particularly relates to a metal layer with at least one spiral groove that is formed on the column body of the antenna apparatus.
2. Description of the Related Art
Due to the development of communication technology, a lot of electronic products that use wireless communication technology have been developed, such as cell phones, wireless Internet devices and personal digital assistants (PDAs), etc. Consumers demand that such wireless communication devices have consistently better and better features and appearance, as well as smaller dimensions so that they are easy to carry around.
For cell phones, the number of receiving frequencies has increased from an original single frequency, to two, to three, and now a fourth. The receiving-signal effect of wireless communication devices is an important index for evaluating wireless communication devices. The antenna apparatus is a key factor to determine the receiving-signal effect of wireless communication devices. Therefore, it is important to develop an antenna apparatus that receives signals effectively and also has a fresh fashionable appearance and a small size.
Referring to FIGS. 1 and 2, a known antenna apparatus A includes a hollow column 1a, a conductive cable 2a, a first copper wire 3a, a copper column 4a, a second copper wire 5a, and an external casing 6a. 
The conductive cable 2a is received into the hollow column 1a, and the conductive cable 2a electrically contacts the hollow column 1a. Moreover, the first copper wire 3a electrically connects between the conductive cable 2a and the copper column 4a. In addition, the second copper wire 5a has a spring structure 50a, and the copper wire 5a is embedded on a top side of the copper column 4a. Furthermore, the external casing 6a entirely covers the hollow column 1a, the conductive cable 2a, the first copper wire 3a, the copper column 4a, and the second copper wire 5a. Finally, as shown in FIG. 2, the antenna apparatus A is installed on an AP (Access Point) P.
However, the spiral structure 50 of the second copper wire 5a often deforms during shipment. The deformation of the spiral coil affects the signal receiving ability and the quality of the antenna. Moreover, due to the structure of the antenna, the dimension of the antenna cannot be shrunk further. In addition, the known antenna apparatus has some defects such as its low frequency bandwidth is narrow.